The present invention relates to door/window magnetic sensor for sensing the opening and closing of a door or window
Prior art door/window magnetic sensing devices use a reed switch so only the open or closed state of the reed switch is known. A magnet must be positioned close to the switching point of a reed switch, which has a limited distance range for switching. The field applied by the magnet to the reed switch may also vary a small amount in a particular installation due to normal amount of play in the door latching mechanism and seal (weather strip). This limited change in position of the magnet relative to the reed switch may lead to a false alarm when a door moves even slightly, for instance, due to a wind storm or due to a barometric pressure change.
Another issue with the traditional reed switch and magnet door sensors is that a would-be thief can simply place a second magnet on the reed switch housing. The second magnet keeps the reed switch in its normal state even when the door is opened. The thief returns later to open the door and goes undetected.
Finally, in many instances mounting a magnet near a traditional reed switch can be difficult as there is uncertainty whether the magnet and reed switch are within an appropriate distance during installation.